The present invention relates to a data communication apparatus, and more particularly to a data communication apparatus having the function of processing in a case where an interruption is generated to one's own station from a third party's station during transmission of data.
A communication system is known which is adapted to transmit and receive image data between facsimile apparatuses, or transmit and receive data by connecting information processing apparatuses including a personal computer by means of telephone lines. In such a communication system, a method of communication in which in a case where a request for line connection is made to a data-transmitting station from a third station, the present communication is interrupted immediately is disclosed in Japanese Patent Application Laid-Open Nos. 63-67868 and 64-86660. In these communication methods, if, during data transmission, an interruption signal has been received from another party or an operator has given an instruction due to a need to effect arbitrary interruption processing, the line is disconnected and data communication is interrupted. Then, after executing predetermining interruption processing, the data transmission is resumed automatically.
However, in a case where the communication which has been subjected to an interruption request is a communication whose content is more urgent, the communication can by no means be interrupted immediately in the manner of this communication method. Accordingly, if cases such as this is taken into consideration, it is inevitable to provide a setting such that the communication with the initial party of communication is continued without responding to the call from the third party.
In the case where the present communication is continued without responding to a call from a third party as described above, the following problems have been encountered.
That is, if a call is made from a third party during communication, there are cases where a disturbance occurs in the transmission data due to the call signal. For instance, if a request for line connection is made from a third party during facsimile communication between two stations, this request is detected by an exchange, and a call waiting signal having a predetermined frequency and an intermittent ringing interval is transmitted to the transmitting station. As a result, there are cases where the transmitted image information is disturbed by this call-waiting signal. Since the call-waiting signal is frequently continued until the line is connected to a third station, it follows that the image information cannot be transmitted properly in the meantime.
In addition, even if the communication is interrupted immediately in response to the call-waiting signal, as a minimum, the image information of the page which was being transmitted during reception of the call-waiting signal is disturbed.
If such a disturbance occurs in the image information, the operator of the receiving station who does not know that an interruption has been generated to the transmitting station due to the call-waiting signal or the like cannot identify the cause, so that the operator will become anxious about it unnecessarily.